Effect of distinct sediments on Florida’s reef corals

This project aimed to identify the impacts of coarse-grain (125–250 µm) and fine-grain (<62 µm) sediments on larval settlement and recruit survival across multiple species of coral found on Florida’s Coral Reef (A. cervicornis, A. palmata, C. natans, D. labyrinthiformis, O. faveolata, and P. clivosa). Overall, fine sediment was a greater deterrent to larval settlement than coarse sediment and species listed under the Endangered Species Act (A. cervicornis, A. palmata, and O. faveolata) were the most susceptible to the burial of substrate regardless of sediment grain size. When coral recruits were buried under different sediment depths of different sediment grain sizes, we found a pattern opposite to larval settlement: coral recruits were more susceptible to 2 Agreement Number C4075A June 2025 coarse sediment than to fine sediment. Furthermore, large recruits were more likely to survive being buried under sediments for ten days than small recruits. Nevertheless, all recruits exhibited a decline in survival probability when buried under 2 and 4 mm of fine and coarse sediment between 25 and 75%. These findings highlight the need to address sedimentary stressors across the Florida Reef Tract to promote future coral recovery via sexual reproduction. These data could be of further use for predicting how future sedimentation events could impact the stock of juvenile corals, allowing managers to address the impact of multiple proposed scenarios. Importantly, these experiments were conducted using sterilized sediment rather than live sediment with diverse microbiomes that are major drivers of sedimentary biogeochemical processes. Therefore, future research should address variation in coral settlement and survival across live sediments from different sources with distinct microbiomes, such as port-derived and reef-derived sediments. Such endeavors would provide more accurate data on the response of reefbuilding corals to sediments that are more representative of what is usually present in the natural environment and introduced by anthropogenic disturbances. 

Main Findings:

Larval settlement assays Burial of settlement substrate severely reduced the potential for the settlement for all coral species tested and fine sediment was more impactful than coarse sediment. Burial of settlement substrate by 2mm of fine sediment decreased the predicted probability of settlement by 10–0%. Burial of settlement substrate by 4mm of fine sediments resulted in complete settlement inhibition for all species. 

Lethal effects of sediment grain size on coral recruits Coarse sediment was more detrimental to recruit survival than fine sediment. Burial under coarse sediment for 10 days severely reduces the survivorship of coral recruits, and size is an important factor that can increase survival probability. Predicted survival probability of 1 cm2 and 4 cm2 corals decreased by 36–68% after 10 days of burial under 4mm of sediment.